code: def check_backward(self, x_data, y_grad):
      x = chainer.Variable(x_data)
      y = self.l(x)
      if self.dilate == 1:
          y.grad = y_grad
      elif self.dilate == 2:
          y.grad = y_grad[:, :, 1:-1, 1:-1]
      y.backward()
  
file_path: chainercv/tests/links_tests/connection_tests/test_separable_conv_2d_bn_activ.py
imports: import unittest
  import chainer
  from chainer.backends import cuda
  from chainer.functions import relu
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links import SeparableConv2DBNActiv
  import numpy
label_desc: Use image node_id 5 for calling the TestSeparableConv2DBNActiv obj's underlying member method code with example usage: obj.check_backward(x_data, y_grad) without return types